A Tachyon Walks into a Bar
by starofoberon
Summary: David Rossi tries to teach Spencer Reid how to tell a joke. A little bitty one-shot rescued challenge from CCOAC.


A/N: This was a rescued CCOAC Challenge from January, 2012. My task was to combine Reid, Rossi, and a resolution for Reid to learn how to tell jokes effectively. A zillion thanks to some of the funniest Mensans I know, especially Kevin, Jamie, Michael, Amy, Terry, and Betsy—you know why, guys!—and a special shout-out to Hank, who edits the Mensa humor newsletter, _The Atrocity._

Thanks as ever to Esperanta, world's greatest beta, whose sense of humor runs the gamut from obscure puns to fart jokes. Plus she makes my writing look good.

**A Tachyon Walks into a Bar...**

David Rossi had been at Reid's for less than an hour, but he felt as though he'd already aged five years. This project was probably the stupidest and the least-well-thought-out New Year's resolution ever, in a lifetime chock-full of stupid and ill-considered notions.

Spencer Reid would never learn to tell a joke, and Rossi was an idiot for wanting to teach him.

"Look," he said to the younger man sitting across the dining room table from him, trying not to sound impatient. "You're not the only genius I know. Not even the only super-genius. And all of them can tell jokes, Reid. _All_ of them. They even tell them _well_. So somewhere up here—" he tapped meaningfully at his own temple "—there's a disconnect going on."

"But it was _funny_," Spencer Reid protested.

"In your own little world," Rossi said. "Trust me, no matter how well educated they are, you line up a million U.S. citizens and only one or two—if that—are gonna get a pun based on the differences between classical and demotic Greek."

Reid's lower lip protruded slightly in the beginning of a pout. "But you liked the one about the pseudoepigraphia."

Rossi's eyes closed in frustration. "No, Reid, I _got_ the one about the pseudoepigraphia. You happened to tell it to a guy whose brother's a professor of biblical studies. There aren't that many of us, and even though I got it, I didn't find it funny. Key word here: _Joke_ equals _funny_. Not _intellectually challenging._ Not _thought-provoking._ Nothing _wrong_ with either of those things," he added hastily, seeing the urge to debate reflected in Reid's posture—honest to God, he was like a war horse or a firehouse dog; some stimuli he just couldn't ignore. "But the point of humor is to get people to _laugh_."

And Mr. Phenomenal IQ looked at him blankly. "Why? What's the payoff?"

"You know better than that, Spencer. Explain to me the physiological causes and theoretical evolutionary advantages of laughter."

Annnnd—he was off and running, citing sources and summarizing research. Man, it was great to debate with a man who, genius or not, could so easily be bamboozled into backing up your arguments for you! Just wind him up, and he'd spit out beautifully organized facts without regard to whether it was his own position or his opponent's he was defending.

Rossi quickly consulted his list of jokes, and when Reid's expository mode ran down, he was ready. "Reid, tell me: Why do computer programmers confuse Halloween and Christmas?"

Spencer stared at him. Finally he said, "Something about dressing up, but…."

_Oh, my God. I have to prompt Spencer Reid. This is a freaking first._ "Think base eight, to start with." When the hint did nothing, Rossi said, "Because OCT 31 = DEC 25."

And Spencer Reid cracked up. He didn't even have the breath to tell Rossi what Dave already knew: that 31 in base eight was 25 in base ten.

In that instant, Rossi realized that he had never seen Genius Boy laugh before. Smile, yes. Grin, certainly. Laugh? Never.

Pressing his advantage, he said, "A Higgs boson walks into a church—"

"Right," Reid said, still recovering from his historic attack of amusement. "That makes perfect sense—it's called the 'God' particle."

But Rossi was far from finished. "The pastor says, 'You're not welcome here,' and the Higgs boson says, 'But without me, how will you have Mass?'"

Reid's features convulsed and he clutched at his sides. _"_Mass," the BAU Expert on Everything chortled. "Of course! Because the Higgs field—"

"Stop," Rossi commanded. Pointlessly, since Reid was making no progress whatsoever in his stab at explaining particle physics. At the moment he looked and sounded less like a triple-PhD than Anderson Cooper in the grips of a giggle fit.

When Reid seemed to be getting his breath back, Rossi said, "What's a tachyon?"

"It's, uh, it's a hypothetical particle that travels faster than light and therefore—"

"_Bzzt__!_ Wrong! Thanks for playing. It's a gluon that isn't quite dry."

Reid looked confused for a second or two, then he was lost in the land of giggles again. He tried, between gasps of "Tacky! Oh, my Lord, tacky!" to say something about Rossi's grasp of theoretical physics, but he was never able to finish. This was a good thing, because Dave would have hated to explain that he'd harvested big-brain jokes from a few big-brain friends for the occasion.

Just as Rossi was gearing up to tell another joke, Reid hauled out his phone and hit speed-dial. "Emily," he said breathlessly, "What's a tachyon?"

After about three seconds, he said, "Sorry, wrong answer. It's a gluon that isn't quite dry."

And he laughed again, and he said, "I know," to Emily.

Then he listened, and said, "I don't—oh, Prentiss!" He laughed again, then said, "Sorry, got to go, have to tell Rossi that one."

He closed off the call and looked at Dave. "I get it!" he said. "It's an unexpected juxtaposition of meanings, one that's jarring and clever enough to trigger a physiological reaction. And the key is that the recipient has to understand all possible meanings in order to appreciate the juxtaposition. Otherwise, there's no opportunity for risibility."

Rossi blinked. "That sounds about right."

"Two atoms are walking along and one says, 'I've lost an electron.' And the other one says, 'Are you sure?' and the first one says, 'Of course—I'm positive.'"

Rossi chuckled, at least partially with surprise. His timing could use some work, but he seemed on the path to humor.

But Reid wasn't done yet. "Well, clearly you know what a tachyon is."

"Ah, yes." He'd looked them up before he tackled the joke project. Hypothetical particles, faster than light, potentially with the ability to time travel.

"What it really is."

Rossi nodded.

"OK, the bartender says, 'We don't serve your kind in here.' A tachyon walks into a bar…."

He really, really had to think about that one, but when he did, he cackled.

"I got that one from Emily," Reid confided happily.

"Hey," Dave said, "what's the difference between an entomologist and an etymologist?"

"Well, one—wait!" Reid's eyes glowed. "I get it. There's a juxtaposition I don't see, so the answer isn't to define them, but to say, 'I don't know, Rossi. What's the difference?'"

Rossi grinned hugely. "The difference is that an etymologist _knows _the difference."

And Reid grinned back. "That's a _good_ one!"

Mission accomplished, baby!


End file.
